Mechanism for transforming the reciprocal movement of a piston into a circular movement of a shaft

ABSTRACT

Device for transforming the alternating motion of a piston into a circular motion of a shaft with the possibility of predetermining the stop time of the piston at each of the two dead centers. It is comprised of an assembly of two pistons connected by two racks alternatingly in mesh with a toothed sector keyed on the shaft. On either side of said sector there is provided a cam of which the groove takes charge of the pistons, through rollers at the two dead centers.

BACKGROUND OF THE INVENTION

The invention relates to the transformation of a reciprocal movementobtained from a piston by the thrust of a fluid, into a rotary movementrecoverable on a shaft or reciprocally.

Such transformation is traditionally obtained by a link-crank assemblywith the drawbacks inherent in this system. In fact, the analysis of theforce exerted on the link reveals a horizontal component, absorbingenergy. In addition, for a constant rotational speed of the shaft, thatof the piston follows a sinusoidal function, whence a reduced meanlinear speed.

In use in thermal engines, the link-crank assembly makes it necessary touse different expedients such as ignition and exhaust advance, movementof the piston in accordance with a rigid mathematical law.

The present invention proposes overcoming these drawbacks and provides adevice for transforming a reciprocal movement into a rotary movementwhich, while being of great mechanical simplicity, allows optimumefficiency to be obtained without requiring the use of ignition andexhaust advance of the thermal engines.

SUMMARY OF THE INVENTION

The device of the invention includes essentially two racks connected tothe piston of the engine and which drive alternately a toothed sectorcarried by the drive shaft, two cams being also carried by the driveshaft and serving as guides for four rollers fixed to the mobilerack-piston assembly.

Advantageously, the second and last but one teeth of each of the racksare partially truncated, as well as the end teeth of this toothed sectorcooperating with the racks.

The profile of the cam is designed so as to provide ignition only at theend of compression and so as to have a variation of the volume of thechamber, so of the pressure of the ideal mixture, during the wholecombustion time.

Furthermore, a better exhaust and filling are obtained during the timewhen the piston is stopped at the end of its stroke, corresponding to azone of the cam concentric with the axis of rotation of the outputshaft.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, one embodiment thereof willbe described hereafter with reference to the accompanying schematicdrawings in which:

FIG. 1 shows a device having two racks cooperating with a toothedsector;

FIG. 2 shows a front and vertical sectional view of one of the camsfixed on the output shaft; and

FIG. 3 shows one embodiment with two opposed pistons.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1 there is shown the device of the invention formed of two racks1, 2 integrally secured to pistons (not shown in this Figure) and movingas a single block for meshing alternately with a toothed sector 3 fixedon the output shaft. In the example chosen, racks 1, 2 have 9 teeth andthe toothed sector 3 integrally secured to the output shaft has 8 teeth,for a pinion of the same modulus having 20 teeth. The second and lastbut one teeth of each rack 1, 2 as well as the end teeth of the toothedsector 3 are truncated, as shown in FIG. 1. This Figure shows thetoothed sector 3 in an intermediate position, separated from racks 1, 2.

To provide drive continuity two cams 4, one of which is shown in FIG. 2,are fixed on the output shaft for taking over. A groove 5 formed in cam4 guides a roller fixed to the piston-rack assembly. Groove 5 is brokendown into five zones:

zone of angle α, corresponding to the simultaneous drive of the ouputshaft by cam and rack at a distance V,

zone of angle β, corresponding to a deceleration of the rack-pistonassembly,

zone of angle γ, stopping of this assembly,

zone of angle δ, acceleration of the assembly,

zone of angle Ω, simultaneous drive by cam and rack at speed -V.

During the end of travel strokes, the possibility of modifying the pathof the groove of the cams allows the speed of movement of the mobileassembly, and so the variation of the volume of the combustion chamberto be controlled at will, depending on the fuel used.

During the rack drive the linear speed of the piston is constant andcorresponds to the mean speed of link-crank drive systems. This linearspeed may therefore be increased, while remaining below the jammingspeed due to the friction of the segments on the cylinders, therotational speed of the output shaft being increased in the sameproportions.

In FIG. 3 has been shown one embodiment with two opposed pistons. Inthis embodiment, two half bodies 6 are assembled together by four bolts7 and sandwich therebetween two bronze slides 8 which guide the tworacks 1, 2 joining the two pistons 9 together. On the output shaft 10are assembled the toothed sector 3 and cams 4, the groove 5 of thesecams driving the pistons 9 through rollers 12 carried thereby. Thecylinders inside which pistons 9 slide are shown by the two caps 13which cover the two half bodies.

The operation will be immediately understood from the prcedingdescription, the movement in one direction of the assembly formed bypistons 9 and racks 2, following the explosion in one of the cylinders,causing one of the racks 2 to mesh with the toothed sector 3 and sorotating shaft 10. At the end of this meshing period, cam 4 cooperateswith the roller 12 of one of the pistons so as to ensure continuity ofthe drive, then the explosion occurs in the other cylinder causing themovement of assembly 9, 2 in the opposite direction and so meshing ofthe other rack 1 with the sector 3 so as to continue the drive or shaft10.

What is claimed is:
 1. A device for transforming a reciprocal movementof a piston into a continuous rotary movement of a shaft, whichcomprises:(a) a pair of pistons, each said piston providing a stroke inan opposite direction; (b) two racks, each rack integral with andtravelling uniformly in response to a stroke from both of pistons; (c)said shaft; (d) a circular grear having a toothed sector fixed to saidshaft and disposed between said two racks, said toothed sector being inmeshing engagement with one of said racks during a stroke from one ofsaid pistons in one direction and in meshing engagement with the otherof said racks during a piston stroke from the other of said pistons inthe opposite direction; (e) two rollers disposed and fixed on oppositefaces of each of said pistons, on the longitudinal axis thereof; and (f)two cams fixed on said shaft, each cam having a groove having fivedifferent zones co-acting with one of said rollers one said zone beingconcentric with the rotational axis of said shaft and corresponding tothe termination of the stroke of one of said pistons, said cams guidingsaid rollers.
 2. Device according to claim 1, wherein the second andlast but one teeth of said racks are partially truncated.
 3. Deviceaccording to claim 1, wherein the end teeth of the toothed sector arepartially truncated.
 4. Device according to claim 2, wherein the endteeth of the toothed sector are partially truncated.